In recent years, transmissive optical elements such as a polarization beam splitter and a bandpass filter have been actively developed. Such a transmissive optical element has been conventionally formed in a multi-layer film structure. However, in order to obtain higher luminance and contrast of a projector or the like, a microscopic three-dimensional hollow structural body formed at a pitch equal to or smaller than that of visible light wavelength has been recently developed. U.S. Patent Application Publication No. 2007/0201135 proposes an optical element having a three-dimensional structure and a method of producing the optical element.
Incidentally, in the method of producing a transmissive micro optical element of U.S. Patent Application Publication No. 2007/0201135, an adhesive is used when a microscopic three-dimensional hollow structural body is bonded to a substrate. However, because the element has a microscopic three-dimensional hollow structure, it is found, when the adhesive is used for bonding to the substrate, that a capillary phenomenon occurs in a gap and the adhesive adheres to the inside of the structural body, which generates fluctuations in refractive index. Therefore, a bonding technology without using the adhesive is desired. However, a structure with the in-plane period shorter than the wavelength of visible light and with a particularly small line width and dot diameter is low in strength, and hence the structural body is damaged when applied with a large load. If a non-contact part is generated between the structural body formed on the substrate and a bonding substrate, incident light may be reflected thereby, thus leading to a possible decrease in optical performance of the optical element. Moreover, a load is concentrated on a contact part, and thus the structural body may be damaged.